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    <H1 CLASS="title">Function Template <CODE>putback</CODE></H1>
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  <DT><A href="#overview">Overview</A></DT>
  <DT><A href="#headers">Headers</A></DT>
  <DT><A href="#reference">Reference</A></DT>
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<A NAME="overview"></A>
<H2>Overview</H2>

<P>
    The function template <CODE>putback</CODE> provides a uniform interface for putting back characters read from models of <A HREF="../concepts/peekable.html">Peekable</A>, for use in the definitions of <A HREF="../concepts/filter.html">Filters</A>.
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<A NAME="headers"></A>
<H2>Headers</H2>

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  <DT><A CLASS="header" HREF="../../../../boost/iostreams/operations.hpp"><CODE>&lt;boost/iostreams/operations.hpp&gt;</CODE></A></DT>
  <DT><A CLASS="header" HREF="../../../../boost/iostreams/putback.hpp"><CODE>&lt;boost/iostreams/putback.hpp&gt;</CODE></A></DT>
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<A NAME="reference"></A>
<H2>Reference</H2>

<A NAME="description"></A>
<H4>Description</H4>

<P>Attempt to putback a character to a given instance of the template parameter <CODE>Peekable</CODE>, returning <CODE>true</CODE> for success.</P>

<A NAME="synopsis"></A>
<H4>Synopsis</H4>

<PRE CLASS="broken_ie"><SPAN CLASS="keyword">namespace</SPAN> boost { <SPAN CLASS="keyword">namespace</SPAN> iostreams {
              
    <SPAN CLASS="keyword">template</SPAN>&lt;<SPAN CLASS="keyword">typename</SPAN> <A CLASS="documented" HREF="#template_params">Peekable</A>&gt;     
    <SPAN CLASS="keyword">bool</SPAN> <A CLASS="documented" HREF="#semantics">putback</A>(Peekable&amp; peekable, <SPAN CLASS="keyword">typename</SPAN> <A CLASS="documented" HREF="../guide/traits.html#char_type_of_ref">char_type_of</A>&lt;Peekable&gt;::type c);

} } <SPAN CLASS="comment">// End namespace boost::io</SPAN></PRE>

<A NAME="template_params"></A>
<H4>Template Parameters</H4>

<TABLE STYLE="margin-left:2em" BORDER=0 CELLPADDING=2>
<TR>
    <TR>
        <TD VALIGN="top"><I>Peekable</I></TD><TD WIDTH="2em" VALIGN="top">-</TD>
        <TD>A model of <A HREF="../concepts/peekable.html">Peekable</A>.
    </TR>
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<A NAME="semantics"></A>
<H4>Semantics</H4>

<P>The semantics of <CODE>putback</CODE> depends on the <A HREF="../guide/traits.html#category">category</A> of <CODE>Peekable</CODE> as follows:</P>

<TABLE STYLE="margin:0,0,2em,2em" BORDER=1 CELLPADDING=4>
    <TR><TH><CODE>category_of&lt;Peekable&gt;::type</CODE></TH><TH>semantics</TH></TR>
    <TR>
        <TD VALIGN="top">convertible to <A HREF="../guide/traits.html#category_tags"><CODE>istream_tag</CODE></A></TD>
        <TD>invokes <CODE>peekable.rdbuf()->putback(c)</CODE> and returns <CODE>true</CODE> if the operation was successful</CODE></TD>
    </TR>
    <TR>
        <TD VALIGN="top">convertible to <A HREF="../guide/traits.html#category_tags"><CODE>streambuf_tag</CODE></A> but not to <A HREF="../guide/traits.html#category_tags"><CODE>istream_tag</CODE></A></TD>
        <TD>invokes <CODE>peekable.sputbackc(c)</CODE> and returns <CODE>true</CODE> if the operation was successful</TD>
    </TR>
    <TR>
        <TD VALIGN="top">convertible to <A HREF="../guide/traits.html#category_tags"><CODE>peekable_tag</CODE></A> but not to <A HREF="../guide/traits.html#category_tags"><CODE>streambuf_tag</CODE></A> or <A HREF="../guide/traits.html#category_tags"><CODE>istream_tag</CODE></A></TD>
        <TD>returns <CODE>peekable.putback(c)</CODE></TD>
    </TR>
    <TR>
        <TD VALIGN="top">otherwise</TD>
        <TD>compile-time error</CODE></TD>
    </TR>
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    Distributed under the Boost Software License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at <A HREF="http://www.boost.org/LICENSE_1_0.txt">http://www.boost.org/LICENSE_1_0.txt</A>)
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